Process for preparing interpolyesters of bibenzoic acid, a hetero-aliphatic acid and an aliphatic glycol, and shaped articles thereof



United States Patent 3,008,930 A PROCESS FOR PREPARING INTERPOLYESTERS OF BIBENZOIC ACID, A HETERO-ALIPHATIC j poration, Philadelphia, Pa., a corporation of Delaware I No Drawing. Filed July 28, 1958, Ser. No. 751,165 6 Claims. (Cl. 26075) This invention relates to new and useful interpolyesters, shaped articles prepared therefrom and methods of preparing the same. More particularly it is directed to unique interpolyesters of bibenzoic acid, an aliphatic glycol and hetero-aliphatic dicarboxylic acid. This invention relates further to films, fibers, molded products, coatings and other shaped articles prepared from the unique interpolyesters described above.

The history of polyesters is a relatively short but active one. Condensation polyesters, while encountered in early researches such as those of Lourenco, Bischofl, Fischer, etc., were not intensively studied until 1928, when Carothers and co-workers began a systematic study of condensation polymerization. Illustrative of Carothers work is U.S. Patent No. 2,071,250 (1937) which discusses some of the previous work in the field and some of the problems in drawing polyesters into fibers. Oarothers produced filaments from his polyesters, but they were lowmelting and lacked hydrolytic stability.

The current prior art describes various linear condensation polyesters derived from dihydroxy compounds and .dibasic acids, such as terephthalic acid, which are capable of being drawn into fibers showing, by characteristic X- ray patterns, orientation along the fiber axis. However, in using a single glycol and single acid to prepare a polyester, one is limited to a fixed crystal structure and melting point since the constitution of the polymer cannot be varied.

In recent years a limited amount of work has been done involving bibenzoic acid and its esters inconnection with homopolyesters. The prior art indicates, however, that this work was not generally fruitful, for a homopolyester of bibenzoic acid and a glycol (e.g. polyethylenebibenzoate) possesses an extremely high melting point making its use in shaped articles entirely impractical, particularly when attempts were made to use has a film or fiber-forming material. Moreover, and ,possibly more important, known polybibenzoates exhibit an extremely high rate of crystallization, making orientation of fibers or films therefrom extremely. difficult and costly, if not impossible, from a commercial standpoint.

This invention overcomes these limitations in providing as one of its objects new and useful highly polymeric interpolyesters of an aliphatic glycol, bibenzoic acid and a hetero-aliphatic acid having valuable properties, including those of being capable of being formed into useful filaments, films, and the like. It is a further object of this invention to provide unique interpolyesters as described above which possess melting points and rates of crystallization which make them amenable to the preparation of new and useful fibers, films, molded products, coatings, other shaped articles and the like. A still further object is the provision of unique interpolyesters having a low degree of solubility in organic solvents. A further object is the provision of new and useful synthetic filaments and films possessing improved moisture regain characteristics. Another object is the provision of new and useful synthetic fibers, film and molded objects having improved dyeing characteristics. A still further object is the provision of a new process for making the unique interpolyesters of this invention. Other objects will appear hereinafter.

The synthetic products according to the present invention are difliculty soluble, usually crystallizable, orientable, highly polymerized interpolyesters of (1) bibenzoic acid, having the general formula:

(2) a hetero-aliphatic dicarboxylic acid having the general formula:

HOOO(RX),,-R'-COOH wherein R and R' are the same or different bivalent straight or branched chain aliphatic hydrocarbon radicals containing 1 to 12 carbon atoms, X is an ether oxygen radical or a snlfone radical and n is an integer of from 1 to 6, and (3) a glycol or dihydric alcohol having the general formula: I I

HOR-OH wherein R is a bivalent straight or branched chain aliphatic hydrocarbon radical containing 2 to 20 carbon atoms.

Some of the polyesters of the present invention possess, among others, the following superior fiber and film properties: (1) controlled melting points over a relatively wide range, i.e. above C., (2) toughness, (3) controlled crystallizability dependent upon thermal and orienting treatment, (4) orientability, (5) pliability and (6) lack of color. Items (1) and (3) are important in order that the fiber or film have good thermal and dimensional stability, as well as orientability, under a variety of conditions. The advantages of toughness, pliability and lack of color are readily apparent. In order that these latter characteristics be attained, the fiber or film forming polymer must not crystallize too rapidly; otherwise it will not be possible to properly orient it. In other words, it must be capable of being easily converted to an amorphous form which can be oriented by cold or hot drawing or other known orienting procedures. On the other hand, the fiber or. film-forming polymer must have latent ability to crystallize, for if it does not it is then brittle toward impact and possesses poor dimensional stability.

In preparing the unique interpolyesters of this invention bibenzoic' acid, or a diester or acid chloride thereof, is reacted with one of the hetero-aliphatic dicarboxylic acids described above, or a diester or acid chloride thereof, and one of glycols described above. An ester interchange reaction is generally preferred since the time required'to form the interpolyesters of this invention is generally considerably less; and/or side reactions can generally be minimized to a greater degree than when the freedi- 'carboxylic acids are employed.

Y The ester interchange method for preparing the interpolyesters of this invention" proceeds in three stages: I. One mole of a mixture of a monomeric diester of bibenzoic acid and a monomeric diester of one of the heteroaliphatic acids described above is reacted in the presence of heat and an ester interchange catalyst with at least two moles of a glycol and a monohydric alcohol is distilled off;

. II. The temperature is gradually raised to bring about polymerization and excess glycol is distilled off; and

I III. Polymerization is driven to completion by gradually reducing the pressure to remove the last traces'of O O O wherein Y is a bivalent hydrocarbon radical as described in (3) above; R and R are same or different hydrocarbonradicals derived from a straight or'branched chain aliphatic primary or secondary monohydric alcohol boiling within the range from about 64 to 215 C.; R ,is hydrocarbon residue of .bibenzoic acid and R is the heterohyd-rocarbon residue of .one of the hetero-aliphatic acids described above in (2).

In a preferred embodiment of this invention, the mixture of monomeric diesters described above (in a ratio of 75 to -95 weight percent of a bibenzoate and .25 to 5 'weigh't. pereent of a hetero-aliphatic dicarboxylate) and a glycol are weighed into a vessel, the ester interchange catalyst added, and a boiling chip introduced. Stage I esterinterchange is then carried-out at atmospheric pressure under nitrogen at a temperature between about 150 and 225 C. (preferably 175 to 200 C.) for about 2 ditions. It is therefore usually necessary to utilize an excess of the glycol, preferably at least two moles of glycol to one mole of mixed diesters. Quantities, substantially larger than about 2 moles of the glycol may be used; however, since they are not necessary, in the interests of economy, they are not recommended.

Examples of some of the various monomeric diesters which can be employed in accordance with the process of the invention include those derived from bibenzoic acid, the hetero-aliphatic acids of this invention and one of the following primary monohydric alcohols: methanol, ethanol, propanol-l, Z-methyl-propanol-l, butanol-l, 2-methyl-butanol 4, 2,2-dimethyl propanol-L pentanol-l, 2-methyl-pentanol-1, Z-methyl-pentanoLS, 3- methylol-pentane, hexanol-l, 2-methyl-hexanol-l, 2-methyl-hexanol-6, heptanol-1, 2-ethyl-hexanol-1, octanol-l, nonanol 1,2,6 dimethyl 3 methylol heptane. Diesters derived from these same acids and secondary monohydric alcohols can be utilized also, e.g. propanol-2, butanol-Z, 2-methyl-butanol-3, pentanol-Z, pentanol-Si, 2- methyl-pentanol-3, 3-methyl-pentanol-2, hex-anol-2, 2,2- dimethyl-butanol-3, 2-methyl-hexanol-3, heptanol-4, octanol-2, decanol-4.

Since in the preferred process, the alcohols from which the diesters are derived are removed from the reaction zone by boiling, it is generally necessary to utilize a glycol having a boiling point higher than that of the alcohol being evolved. Examples of some of the glycols described in (3') above are as follows:

Ethylene, 'trimethylene, tetramethylene, pentamethylene, hexamethylene, decamethylene glycols, 1,2-propylene glycol, '2,2-dimethyl-l,3-propane diol, 2,2,3,'3-tetramethyl-1,4-

butanediol, 2-bu'ten-l,4-diol, 2-heXen-l,6-diol, '3-octen-l,8 diol, '2-penten-l,4-diol, 3-hepten-l,5-diol, etc.

The following are illustrative of some of the heteroaliphatic dicarboxylic acids useful for the purpose of 1 this invention: diglycollic acid, fl,fl'-oxy-dipropionic acid,

to 10 hours, distilling oifmonohydric alcohol. Polymerization is .thenbrought about in stage .(II) .by raising the temperature graduallyto between about 200 and 400 .C. (preferably about 260 to 290 C.) over a period of about /2 to 2. hours, continuing polymerization for a period of about /2 to 3 hours at this temperature and distilling off excess glycol. In stage (III) pressure is gradually reduced to below about 5 mm. (preferably'OQZ to 0.5) over a period of about /2 to 4 hours (preferably about 1 to '2 hours), followed by continued heating at this elevated temperature and reduced pressure .for a period of aboutZ to 10 hours. Inthis latter step the last traces of the glycol are distilledoif and there'action mixture becomes progressively more viscous.

The specific temperatures and heating periods may vary .over wider ranges than those outlined above depending .onzthe observed rate ofreaction. In cases Where reaction becomes sluggish, higher temperature and/ or longer periods of time will be employed. In those cases where the polymer is solidified, or begins to solidify before it is apparent all glycol has'been removed,- the temperaiuretand/or theheatingperiod are increased. The conditions can .be varied considerably depending upon the *degree of the polyesterification desired, the ultimateproperties sought, stability of the polyester being produced and use for which the product is intended. When the desired viscosity is reached under these conditions in stage (III), evacuation and heating are discontinued, an inert gas admitted, the vessel allowed to cool to approximately room temperature and the polyester removed.

Intheory a total of only one mole of the glycol is necessary to-:effect complete .polyesterification with one mole of the mixed monomeric diestersof bibenzoic-and one of the heteroaliphatic acids. However, in practice, it is diflicult to attain complete reaction under these con- -B,)3'-oxy-bis-'(fi-methyl-propionic acid), 'y,' '-oxy-dibutyric acid, 6,a-oxy-divaleric acid, -carboxymethoxy-butyric acid, q carboxyet'hoxy-butyric acid, a-carboxyethoxy-va- 'leric acid, -6-carboxypropoxy-valeric acid, 'y,'y'-sulfonyldibutyric acid, on carboxymethoxyethoxy acetic acid (i-.e. HOOCCH -OCH -CH --OCH COOH) "etc. The properties of films, fibers, or other molded objects which constitute a preferred embodiment of this invention vary greatly depending in a large "measure upon the identity'of the glycol utilized to form the interpolyes'ter. Thus melting points, degree of 'crystallinity, rate-of crystallizing, etc. will vary considerably. In a 'like manner, the quantity, and, to a lesser degree, the identity of the acid described above in. ('2) can cause substantial variation in the properties of the interpolyesters of this invention. Accordingly, although the use of'bibenzoic acid in a quantity in the range of 75 to 95 weight percent is generally satisfactory, a range of '75 to weight percent is generally preferred where formation of films or fibers is contemplated.

The catalytic. condensing agents or ester-interchange catalyst which may be employed "are conventional ones and include, forexample, the alkali metals, the alkaline earth metals; the oxides, carbonates, 'andborates of these two groups of metals, the one to six carbon alkoxide's of these two'groups of metals; magnesium, zinc, and manganese; the oxides of these 'metal's; zinc borate; the lsulfates, phosphates and acetates of zinc, cadmium, magnesium, aluminum and copper; li'tha'rge or a combination of litharge with (antimony trioxide and triphenyl phosphite as described in US. Patent No. 2,650,213; compounds of the formula:

wherein M is .an alkali metal, e.g. lithium, sodium, or potassium, and R is an alkyl radical containing" from l 19 6 carbon atoms; R can be derived-from a lower aliphatic alcohol such as methyl, ethyl, propyl, n-butyl, isobutyl, n-amyl, etc., as described in US. 2,720,506; a composition consisting of lithium hydride and a glycolsoluble organic salt of cadmium, magnesium, or zinc as described in U. S. Patent No. 2,681,360.

From about 0.005% to about 0.2% of such catalysts based on the weight of diester monomer being condensed may be employed. Higher or lower percentages may also be employed. Generally, from about 0.01% to about 0.05% of the catalytic condensing agent can be advantageously employed, based on the weight of dibasic acid diester being condensed. As will be apparent to those skilled in the art, it is generally advantageous from a cost standpoint to utilize the minimum quantity of one of the above catalysts which efiect optimum results. Obviously, however, quantities larger or smaller than those outlined above will be employed by those skilled in the art where needed, e.g. to accelerate or decelerate rate of reaction, to modify properties--luster, molecular weight, tenacity, etc.

The reaction can be carried out in the presence or absence of a solvent, preferably the latter. Illustrative of such solvents are inert high boiling compounds, such as diphenyl ether, diphenyl, mixed tolyl sulfones, chlorinated naphthalene, chlorinated diphenyl, dimethyl sulfolane, etc.

It is essential to exclude oxygen and moisture at all stages of the condensation reaction. Otherwise discoloration, low molecular weight, and/ or insolubilization of the polyester results. Inert atmospheres which can advantageously be employed include nitrogen, hydrogen, helium, etc. The exclusion of moisture is readily effected by employing substantially anhydrous reactants.

The interpolyesters of this invention can be formed into filaments or films by conventional melt extrusion procedures. For example, the interpolyesters can be melt extruded vertically at a melt temperature of approximately 25 C. above the melting point of the interpolyester followed by immediate quenching and orientating.

Although illustrated in the preferred embodiment as a batch process, the interpolyesters of this invention can be produced by the continuous methods also; for example, the required amounts of the several reactants and catalyst can be continuously metered into the reaction vessel, maintained therein for the required reaction time under the required reaction conditions of temperature and pressure and then continuously drawn 0E.

The following examples are not given by way of limitation, the scope of the invention being determined by the appended claims.

Example 1 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 9.24 grams of diethyl bibenzoate, 3.54 grams diethyl diglycollate and 6.51 g. ethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then beated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in a thin mobile clear liquid which on cooling solidified to a white opaque pasty solid. The vessel was gradually heated to 260 C. over a 1 hour period with distillation of ethylene glycol. The polymerization temperature was maintained at 260 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 4 hours. The polymer thus produced was a dark brown colored liquid which crystallized to a dark tan opaque brittle solid on cooling.

Example 2 A polymerization vessel fitted with an exit tube, water cooled I condenser and a water cooled receiver was charged with 14.32 grams of diethyl benzoate, 2.28 grams diethyl diglycollate and 8.119 g. ethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 260 C. over a 1 hour period with distillation of ethylene glycol. The polymerization temperature was maintained at 260 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 4 hours. The polymer thus produced was a dark tan solid, having a birelfringent melting point of 341 C.

Example'3 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.32 grams (0.048 mole) diethyl bibenzoate, 2.28 grams (0.012 mole) diethyl diglycollate and 15.60 g. (0.132 mole) hexamethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 260 C. over a 1 hour period. The polymerization temperature was maintained at 260 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a moderately viscous light straw colored liquid which crystallized to a white opaque hard solid on cooling. The polymer had a birefringent melting point of 201 C.

Example 4 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.32 grams (0.048 mole) diethyl bibenzoate, 2.28 grams (0.012 mole) diethyl diglycollate and 13.75 g. (0.132 mole) neopentylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 4 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired prod-.

ucts resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was 7 gradually heated to 260 C. over a .1 hour period. The polymerization temperature was maintained at 260 "C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for'an "additional 4 hours. The

polymer thus produced was a 'dark'brown colored liquid which solidified to an amber transparent solid on cooling.

We claim:

1. A filament and film forming linear interpolyester melting above 140 C. of'comp-onents consisting essentially of a mixture, of dicarboxylicacids and at least two mols per mol of mixed acids of a glycol having the general formula wherein R ,is a bivalent aliphatic hydrocarbon radical containing 2 to carbon atoms, said mixture of acids consisting essentially of from to by weight of p,p-bibenzoic acid and from 25 to 5% by weightof a hetero-aliphatic acid having the general formula 3. The filament and film forming linear interpolyester of claim 2 wherein the glycol is ethylene glycol and the hetero-aliphatic acid is diglycollic acid.

'4. The process of preparing a filament and film forming linear interpolyestermeltin-g above C. which comprises reacting components consisting essentially of a mixture of lower alkyl diesters of dicarboxylic acid and at least two mols per mol of mixed diesters of a glycol having the general formula wherein R and R" are aliphatic hydrocarbon radicals containing 1 to 12 carbon atoms and n is an integer of from 1120 2, said reaction takingplace at a temperature above C. in 'the presence of an ester-interchange catalyst and in the absence of oxygen and-moisture.

5. The process of claim 4 wherein the initial reaction temperature iskept from 150 to 225 C. until no further alcohol is liberated and thereafter the temperature is raisedto from 200 to 400 C. with a gradual reduction of reaction pressure to less than 5 mm. of mercury.

45. The process of claim 5 wherein the initial temperature ranges from to200 -C., thetemperature is raised to from 260 to 290 'C. and the pressure is reduced to fromOZ to 0.5 mm. of mercury.

Snyder Dec. 2 3,, 1952 Caldwell etal Dec. 20, 1955 

1. A FILAMENT AND FILM FORMING LINEAR INTERPOLYESTER MELTING ABOVE 140*C. OF COMPONENTS CONSISTING ESSENTIALLY OF A MIXTURE OF DICARBOXYLIC ACIDS AND AT LEAST TWO MOLS PER MOL OF MIXED ACIDS OF A GLYCOL HAVING THE GENERAL FORMULA 